In my research, I design computational routes to explore the emergent behaviour of nonequilibrium, disordered systems. This has led me to contribute in a wide range of areas, from materialscience to animal behaviour, from transport to physiology.
Collective behaviour and active matter
Active matter ecompasses systems that dissipate energy locally, for example, via self-propulsion. These nonequilibrium routes lead to new phenomena, e.g. pattern formation and motility-induced phase separation. The study of active systems is strongly inspired by living matter, so colonies of ants, groups of birds, and schools of fish can all be seen through the same lens. Also, artificial active matter can be realised in the lab, for example, with robot swarms or self-catalytic colloidal particles, to have a precise control on the interactions and governing parameters.
In my research I investigate both fundamental problems (such as the wetting properties of active fluids) and applications, using particle-based computer simulation and in close collaboration with experimentalists.
Here are some questions that I have addressed:
- Can we tune the wetting behaviour of active fluids? [post, Phys Rev Lett article, Physics Synopsis]
- Does age affect the emergence of collective behaviour in animals, for example, in Zebrafish? [post, PLoS Comput Bio article]
- How cooperative and multi-body is self assembly in model active fluids? [post, Phys Rev Lett article]
Dynamic arrest and glasses
If you happen to deal with a dense, disordered system there are strong chances that it will display features of so called “glassiness”, the most striking of which is dynamic arrest: the progressive slowing down of the dynamics upon coolingg (or increasing the density) with limited structural changes.
Understanding glassiness helps us with many different problems: from material science (new disordered solids, like metallic glasses) to morphogenesis (where dense layers of cell cooperate to give rise to functional tissues). The tools and frameworks developed to understand glassy behaviour are employed to reveal common mechanisms across length and time scales and discover new physics.
A distinctive feature of dynamic arrest is the emergence of strong dynamical heterogeneities, i.e. inhomogeneous distributions of the mobility in space. The origin of such heterogeneity is debated, and my work explored extensively through advanced simulations its relationship with structural and geometrical features. Working with experimentalists, I have tested these ideas to see how they play out in the real world.
Questions that I have addressed include:
- how can we connect static and dynamic theories of the glass transition? [post, Phys Rev X article]
- does the microstructure change when approaching the glass transition in experiments? [post, Nat Comm article]
- how important is geometry and frustration in the relaxation of glassy liquids? [post, Phys Rev Lett article]
Structure and metastability
Soft matter is the study of materials where the relevant energy scale is of the same order of the tehrmal fluctuations. This means that energy and entropy have comparable roles in defining the emrgence of the material properties. Soft materials a re typically complex and are everywhere around us (e.g. food and drugs) and in many ways we can think that many parts of our body is made of them, from the stream of blood cells in the veins to the growth of tissues and bones.
In my work I focussed on the emergence of structure in these complex materials, with a particular attention to the local, micro-structural properties, and often working directly on the analysis of experimental data (where advcanced 3D image analysis techniques and machine learning turn out to be very useful).
A few example questions that I have addressed include
- how to characterise the gene-induced modifications in bone mineral density of model organisms? [post, Bone research article]
- how does shearing lead to amorphisation in perfect crystals? [post, Soft Matter article]
- how does gelation change at very high dilutions? [post, J Chem Phys article]
Transport models
Biological transport processes in cells take place on substrates that are often coupled to the active motion of macromolecular complexes, such as motor proteins on microtubules or ribosomes on mRNAs. Inspired by biological processes such as protein synthesis by ribosomes and motor protein transport, we have discussed the concept of localized dynamical sites coupled to a driven lattice gas dynamics. We investigated the phenomenology of transport in the presence of dynamical defects and found a regime characterized by an intermittent current and subject to severe finite-size effects. Our results demonstrate the impact of the regulatory role of the dynamical defects in transport not only in biology but also in more general contexts.
Transport is aa much more general problem as well: during my master degree, I have been working at the modelling of the traffic flow fundamental graph in a town. See my master thesis (in Italian).
Francesco Turci 